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EE M250B / MAE M282 / BME M250B
Case Study 3: Grating Light Valve (GLV) Reference: • Chapter 20 of Senturia • http://www.siliconlight.com • D. Bloom, “The Grating Light Valve: revolutionizing display technology,” IS&T/SPIE Symposium on Electronic Science and Technology (2/12/97) • D. T. Amm, R. W. Corrigan, “Grating Light Valve ä Technology: Update and Novel Applications,” the Society for Information Display (SID) 1998 Symposium panel Reflective Light Valves (5/19/98)
M. C. Wu
1
EE M250B / MAE M282 / BME M250B
Tilting Micromirror and Grating Light Valve
• •
Reflection Broadband Large displacement at mirror edge – Typically µsec time response
• •
• •
Angle modulated by voltage Intensity remains constant
• •
M. C. Wu
2
Diffraction Wavelength dependent Displacement ~ 0.25 * wavelength – Potential high speed operation (10’s nsec) Angle fixed by lithography Diffracted intensity varied by voltage
EE M250B / MAE M282 / BME M250B
Grating Light Valve Technology Silicon Light Machine a)
Beams up, reflection
Silicon Nitride Beam λ/2
b)
Beams down, diffraction
Silicon Dioxide Posts λ/4
• • •
Simple fabrication process, “color” ready Small moving distance (1/4 wavelength), high mechanical resonance frequency (> MHz), fast switching Stiction (?) Ref: O. Solgaard, F.S.A. Sandejas, and D.M. Bloom, Optics Letters, Vol. 17, p.688, 1992.
M. C. Wu
EE M250B / MAE M282 / BME M250B
GLV Diffraction Efficiency
Diffractivity of the first order as a function of wavelength for an “up pixel with 550 nm design wavelnegth
Apte, Sandejas, Banyai, Bloom, Solid-State Sensor and Actuator Workshop, p. 1 (1994)
M. C. Wu
4
EE M250B / MAE M282 / BME M250B
Gap Closing Actuator Increasing Voltage
Force
Electrostatic Force Spring Force
t Displacement
2t/3
Felec = Fspring
ε 0V
2
Area 2 (t − z ) 2 = −k ⋅ ( z − t ) ⋅
Pull-in when the actuator moves over 1/3 of the original gap spacing
M. C. Wu
5
EE M250B / MAE M282 / BME M250B
Transfer Characteristics of GapClosing Actuator
Displacement
Bistable Regime
Pull-in voltage
VP = Analog Regime
Voltage Pull-in Voltage
M. C. Wu
6
8⋅ k ⋅t3 27ε ⋅ Area
EE M250B / MAE M282 / BME M250B
Grating Light Valve Technology Silicon Light Machine http://www.siliconlight.com
• •
Mechanical resonance frequency > 1 MHz Switching time ~ 100 nsec Ref: O. Solgaard, F.S.A. Sandejas, and D.M. Bloom, Optics Letters, Vol. 17, p.688, 1992.
M. C. Wu
EE M250B / MAE M282 / BME M250B
Color-Oriented Sub-pixels for GLV
M. C. Wu
8
EE M250B / MAE M282 / BME M250B
Head Mount Display using a GLV and 3 LED’s
M. C. Wu
9
EE M250B / MAE M282 / BME M250B
Second-Generation GLV
M. C. Wu
10
EE M250B / MAE M282 / BME M250B
Second-Generation GLV
Compatible with CMOS process, can be built in standard CMOS foundry
M. C. Wu
11
EE M250B / MAE M282 / BME M250B
Photograph of GLV
M. C. Wu
12
EE M250B / MAE M282 / BME M250B
On-Chip Encapsulation of GLV
M. C. Wu
13
EE M250B / MAE M282 / BME M250B
Switching Dynamics of GLV
M. C. Wu
14
EE M250B / MAE M282 / BME M250B
High Efficiency Display Using One GLV and a Color Wheel
• Collect both +1 and -1 diffraction orders to increase the efficiency (81%) • Collecting more orders (± ± 1 and ± 3) 90% efficiency
M. C. Wu
15
EE M250B / MAE M282 / BME M250B
3-GLV Projection System for Large Screen Display
M. C. Wu
16
EE M250B / MAE M282 / BME M250B
Stiction Issue Restoring Force:
Sticking Force:
Stress
FRe storing ∝
Beam
FSticking ∝ Contact
Length
Area
Self-Aligned Sidewall Rail:
•
Engineering Strategy – Increasing restoring force by employing tensile stress in nitride film – Minimize sticking force by • Microscopic surface roughening • Macroscopic surface patterning
M. C. Wu
17
EE M250B / MAE M282 / BME M250B
Tensile Stress in Doubly-Supported Beam (Ref: Senturia, Chap. 9.6) •
•
Euler Beam Equation:
EI
d 4w d 2w − (σ 0WH ) 2 = q 4 dx dx E: Young’s modulus I : Bending moment w: Vertical displacement x: Lateral displacement σ0: Axial stress W, H: width and thickness of beam q: External load
M. C. Wu
When the beam is straight, axial stresses produce no net horizontal force As soon as the beam is bent, there is a net vertical force on the beam – Additional restoring force
k stress− free =
k with− stress =
qL 32 EWH 3 = w max L3
4N L cosh( k0 L 2) − 1 −2 2 k0 sinh( k 0 L 2)
N = σ 0WH 18
k0 =
12 N EWH 3
EE M250B / MAE M282 / BME M250B
Calculated Beam Displacement for Various Axial Tensile Stress Beam dimension: 2x2x100 um3
Higher Stress M. C. Wu
Higher Stiffness 19
EE M250B / MAE M282 / BME M250B
Effect of Stress on Switching Voltage
Apte, Sandejas, Banyai, Bloom, Solid-State Sensor and Actuator Workshop, p. 1 (1994)
M. C. Wu
20
EE M250B / MAE M282 / BME M250B
Third-Generation GLV
• • • • •
M. C. Wu
Noncontact device Operate in analog regime Grey scale controlled by height 1-D array Use external scanner in the orthogonal direction for 2-D display
21
EE M250B / MAE M282 / BME M250B
GLV Pixels • • • • •
25 um pixel 6 ribbons (tensile stressed SiN + Al) 100 um long 125 nm thick 650 nm air gap
Ribbon is longer than the pixel creating 100% diffraction region in the center
Total Pixel Efficiency =
= M. C. Wu
Diffraction efficiency (81%) * Ribbon/Gap Fill Factor (95%) * Aluminum reflectivity 70% 22
EE M250B / MAE M282 / BME M250B
Analog Response of GLV
Contrast of individual devices: 4000 to 1
M. C. Wu
23
EE M250B / MAE M282 / BME M250B
Dynamic Response of GLV • •
•
M. C. Wu
24
Fast GLV response ~ 20 nsec Critical damping to minimize ringing – Proper design of drive electronics circuits – Ambient pressure – Tuning GLV device 1 µsec switching time – 1920 x 1080 HDTV @ 96 Hz refresh rate
EE M250B / MAE M282 / BME M250B
1-D GLV Array and Module
GLV Module with 4 custom IC’s for digitalto-analog conversion
1-D GLV array on 6-inch wafer
1-D GLV chip (1088 pixels)
M. C. Wu
25
EE M250B / MAE M282 / BME M250B
Linear GLV + 1D Scanning
K.E. Petersen (IBM) 1977
M. C. Wu
Silicon Light Machine www.siliconlight.com
26
EE M250B / MAE M282 / BME M250B
Total Efficiency of Scanned Linear GLV Display •
•
M. C. Wu
A color channel efficiency (40 to 50%) is product of – Laser-to-GLV efficiency ~ 90% – GLV pixel efficiency ~ 70% – Projection lens throughput ~ 95% – Scanner duty cycle ~ 90% Laser source is needed
27
EE M250B / MAE M282 / BME M250B
Scanned Linear GLV Calibration
M. C. Wu
28
EE M250B / MAE M282 / BME M250B
Telecommunications Applications
Dynamic Spectral Equalizer (DSE)
Reconfigurable Channel Blocking Filter
M. C. Wu
Dynamic Gain Equalizer
29
Case Study 3: Grating Light Valve (GLV) Reference: • Chapter 20 of Senturia • http://www.siliconlight.com • D. Bloom, “The Grating Light Valve: revolutionizing display technology,” IS&T/SPIE Symposium on Electronic Science and Technology (2/12/97) • D. T. Amm, R. W. Corrigan, “Grating Light Valve ä Technology: Update and Novel Applications,” the Society for Information Display (SID) 1998 Symposium panel Reflective Light Valves (5/19/98)
M. C. Wu
1
EE M250B / MAE M282 / BME M250B
Tilting Micromirror and Grating Light Valve
• •
Reflection Broadband Large displacement at mirror edge – Typically µsec time response
• •
• •
Angle modulated by voltage Intensity remains constant
• •
M. C. Wu
2
Diffraction Wavelength dependent Displacement ~ 0.25 * wavelength – Potential high speed operation (10’s nsec) Angle fixed by lithography Diffracted intensity varied by voltage
EE M250B / MAE M282 / BME M250B
Grating Light Valve Technology Silicon Light Machine a)
Beams up, reflection
Silicon Nitride Beam λ/2
b)
Beams down, diffraction
Silicon Dioxide Posts λ/4
• • •
Simple fabrication process, “color” ready Small moving distance (1/4 wavelength), high mechanical resonance frequency (> MHz), fast switching Stiction (?) Ref: O. Solgaard, F.S.A. Sandejas, and D.M. Bloom, Optics Letters, Vol. 17, p.688, 1992.
M. C. Wu
EE M250B / MAE M282 / BME M250B
GLV Diffraction Efficiency
Diffractivity of the first order as a function of wavelength for an “up pixel with 550 nm design wavelnegth
Apte, Sandejas, Banyai, Bloom, Solid-State Sensor and Actuator Workshop, p. 1 (1994)
M. C. Wu
4
EE M250B / MAE M282 / BME M250B
Gap Closing Actuator Increasing Voltage
Force
Electrostatic Force Spring Force
t Displacement
2t/3
Felec = Fspring
ε 0V
2
Area 2 (t − z ) 2 = −k ⋅ ( z − t ) ⋅
Pull-in when the actuator moves over 1/3 of the original gap spacing
M. C. Wu
5
EE M250B / MAE M282 / BME M250B
Transfer Characteristics of GapClosing Actuator
Displacement
Bistable Regime
Pull-in voltage
VP = Analog Regime
Voltage Pull-in Voltage
M. C. Wu
6
8⋅ k ⋅t3 27ε ⋅ Area
EE M250B / MAE M282 / BME M250B
Grating Light Valve Technology Silicon Light Machine http://www.siliconlight.com
• •
Mechanical resonance frequency > 1 MHz Switching time ~ 100 nsec Ref: O. Solgaard, F.S.A. Sandejas, and D.M. Bloom, Optics Letters, Vol. 17, p.688, 1992.
M. C. Wu
EE M250B / MAE M282 / BME M250B
Color-Oriented Sub-pixels for GLV
M. C. Wu
8
EE M250B / MAE M282 / BME M250B
Head Mount Display using a GLV and 3 LED’s
M. C. Wu
9
EE M250B / MAE M282 / BME M250B
Second-Generation GLV
M. C. Wu
10
EE M250B / MAE M282 / BME M250B
Second-Generation GLV
Compatible with CMOS process, can be built in standard CMOS foundry
M. C. Wu
11
EE M250B / MAE M282 / BME M250B
Photograph of GLV
M. C. Wu
12
EE M250B / MAE M282 / BME M250B
On-Chip Encapsulation of GLV
M. C. Wu
13
EE M250B / MAE M282 / BME M250B
Switching Dynamics of GLV
M. C. Wu
14
EE M250B / MAE M282 / BME M250B
High Efficiency Display Using One GLV and a Color Wheel
• Collect both +1 and -1 diffraction orders to increase the efficiency (81%) • Collecting more orders (± ± 1 and ± 3) 90% efficiency
M. C. Wu
15
EE M250B / MAE M282 / BME M250B
3-GLV Projection System for Large Screen Display
M. C. Wu
16
EE M250B / MAE M282 / BME M250B
Stiction Issue Restoring Force:
Sticking Force:
Stress
FRe storing ∝
Beam
FSticking ∝ Contact
Length
Area
Self-Aligned Sidewall Rail:
•
Engineering Strategy – Increasing restoring force by employing tensile stress in nitride film – Minimize sticking force by • Microscopic surface roughening • Macroscopic surface patterning
M. C. Wu
17
EE M250B / MAE M282 / BME M250B
Tensile Stress in Doubly-Supported Beam (Ref: Senturia, Chap. 9.6) •
•
Euler Beam Equation:
EI
d 4w d 2w − (σ 0WH ) 2 = q 4 dx dx E: Young’s modulus I : Bending moment w: Vertical displacement x: Lateral displacement σ0: Axial stress W, H: width and thickness of beam q: External load
M. C. Wu
When the beam is straight, axial stresses produce no net horizontal force As soon as the beam is bent, there is a net vertical force on the beam – Additional restoring force
k stress− free =
k with− stress =
qL 32 EWH 3 = w max L3
4N L cosh( k0 L 2) − 1 −2 2 k0 sinh( k 0 L 2)
N = σ 0WH 18
k0 =
12 N EWH 3
EE M250B / MAE M282 / BME M250B
Calculated Beam Displacement for Various Axial Tensile Stress Beam dimension: 2x2x100 um3
Higher Stress M. C. Wu
Higher Stiffness 19
EE M250B / MAE M282 / BME M250B
Effect of Stress on Switching Voltage
Apte, Sandejas, Banyai, Bloom, Solid-State Sensor and Actuator Workshop, p. 1 (1994)
M. C. Wu
20
EE M250B / MAE M282 / BME M250B
Third-Generation GLV
• • • • •
M. C. Wu
Noncontact device Operate in analog regime Grey scale controlled by height 1-D array Use external scanner in the orthogonal direction for 2-D display
21
EE M250B / MAE M282 / BME M250B
GLV Pixels • • • • •
25 um pixel 6 ribbons (tensile stressed SiN + Al) 100 um long 125 nm thick 650 nm air gap
Ribbon is longer than the pixel creating 100% diffraction region in the center
Total Pixel Efficiency =
= M. C. Wu
Diffraction efficiency (81%) * Ribbon/Gap Fill Factor (95%) * Aluminum reflectivity 70% 22
EE M250B / MAE M282 / BME M250B
Analog Response of GLV
Contrast of individual devices: 4000 to 1
M. C. Wu
23
EE M250B / MAE M282 / BME M250B
Dynamic Response of GLV • •
•
M. C. Wu
24
Fast GLV response ~ 20 nsec Critical damping to minimize ringing – Proper design of drive electronics circuits – Ambient pressure – Tuning GLV device 1 µsec switching time – 1920 x 1080 HDTV @ 96 Hz refresh rate
EE M250B / MAE M282 / BME M250B
1-D GLV Array and Module
GLV Module with 4 custom IC’s for digitalto-analog conversion
1-D GLV array on 6-inch wafer
1-D GLV chip (1088 pixels)
M. C. Wu
25
EE M250B / MAE M282 / BME M250B
Linear GLV + 1D Scanning
K.E. Petersen (IBM) 1977
M. C. Wu
Silicon Light Machine www.siliconlight.com
26
EE M250B / MAE M282 / BME M250B
Total Efficiency of Scanned Linear GLV Display •
•
M. C. Wu
A color channel efficiency (40 to 50%) is product of – Laser-to-GLV efficiency ~ 90% – GLV pixel efficiency ~ 70% – Projection lens throughput ~ 95% – Scanner duty cycle ~ 90% Laser source is needed
27
EE M250B / MAE M282 / BME M250B
Scanned Linear GLV Calibration
M. C. Wu
28
EE M250B / MAE M282 / BME M250B
Telecommunications Applications
Dynamic Spectral Equalizer (DSE)
Reconfigurable Channel Blocking Filter
M. C. Wu
Dynamic Gain Equalizer
29
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